1. Sokka is the oldest child of Chief Hakoda, only boy, and a waterbender. He grows up knowing that it’s his job, no not his job, his purpose in life to protect his family and his village, especially his sister. He also grows up knowing it’s his fault his and Katara’s mother is dead.
2. To say Sokka has mixed feelings about his waterbending is a massive understatement. It lost him his mother, but someday he could use it to help his sister and grandmother. His sister envies him for it, but he can’t do much with it, and this magic water stuff often causes way more trouble than it’s worth.
3. Meanwhile Katara grows up a typical Southern Water Tribe girl, just as in canon, fiercely determined, fiercely loving, mothering her brother, and at times deeply resenting thr amount of housework she does in proportion to her brother. This resentment all comes to a head in a colossal fight after the two of them get boat-wrecked on an iceflow, in which she yells to him about washing his dirty socks, and the way he never does anything, and he yells back about being the only boy and waterbender and how he doesn’t think he can protect everybody, and he’s really scared, and uh oh, he just cracked open an iceberg with an Avatar inside.
4. Katara nearly stays with the Kyoshi Warriors. Sokka is less inclined to learn from them in this universe, because while they beat him handily and he embarrasses himself in front of Suki, they can’t help him learn to control his bending, which is his big preoccupation. He does however make Suki a very nice apology. Katara on the other hand is enthralled. Here are a band of female warriors trusted by the village to protect them. They are respected and powerful, and clearly formidable warriors. She trains with them and is reluctant to leave. But she knows if she stays, Sokka will stay, and he needs to go to the North Pole, so they journey on.
5. Sokka is a boy, which means Pakku has no problem training him. But Katara finds herself quickly demoted, from the Avatar’s companion and a warrior in her own right, to just the sister of the Avatar’s waterbender. This grates. And it grates worse when she is dismissed as a warrior and told to keep the princess company during the seige. However, when she takes on the Prince of the Fire Nation in defense of Princess Yue and the Avatar, and wins, the Northerners start treating her, and her brother very differently. If only there wasn’t that undertone of “southern barbarian freak” to it. And then there’s the problem Sokka has trying to explain that he’s a natural healer.